Method of producing a rustless iron alloy



- ac claims reamed June 12-, 1923.

*NITED STATES PATENT- OFFICE.

winson nnnnnrr, or WELLINGTON, NEW ZEALAND.

METHOD or'raonucme a RUSTLESS moi: ALLOY.

No Drawing.

certain new and useful Improvements in Methods of Producing a RustlessIron Alloy, of which the following is a specification. This inventionrelates to rustless iron and stainless steel and the process forproducing the same.

One object of the invention is to produce rustless iron or stainlesssteel at a comparatively low cost by developing the same directly fromores or the use of iron or steel l5 scrap, or a combination of scrap andpig iron, by a series of continuous operations while the componentmetals are in a molten state, thus obviating the necessity of previously. refining the different metals that go to make up the completedalloy, or the necessity of producing low carbon ferro chromium as aseparate article and re-melting'the'same in combination with iron,steel,

or scrap. -With these and other objects in view which will appear as thedescription proceeds, this invention consists in the novel featureshereinafter described, and MORE particularly pointed out in the appendedThe use of the following equipment is essential to enable me to carryout my continuous rocess as herein stated:

Blast rnace.For,thereduction of iron 8a fromits ore. I

.' Bessemer converter.-For partially refining reduced molten metal.

Monel metal, manganese and the like.

I Application filed December 4, 1922. Serial No. 604.899.

with upper and bottom electrodes. (1 find the Greaves-Etchell electricfurnace specially suitable to my requirements, but I do not confinemyself solelyto its use.)-

The hearths of the electric furnaces should be composed of basicmaterials.

In producing the base of the rustless iron or stainless steel, onemethod I adopt is to reduce the iron from its ore in the blast furnacein the usual manner employed for 00 the production of pig iron. Thereduced I iron while in a molten state is then transferred to theconverter and subjected to the bessemerizing process until interruptedat a given stage. Molten metal from the cu- 4 pola may be employed forthis purpose. The metal is then transferred while in a molten state tothe combination electric furnace for the final refining and deoxidizingprocess at the one and the same time.

Additional metals or ferro alloys may be' added during the finalrefining rocess to suit requirements, such as molyb enum, vanadium,titanium, tungsten, copper, nickel,

For an alloy containing percentages of nickel and copper I prefer to addthe same in combination form, for example, in the form of Monel metal.

If scrap or a combination of scrap and 8 pig iron is. employed the sameis melted and re ned to requirements by the aid of slags in the basicopen hearth furnace in the usual manner emplo .ed for ingotiron or steelmanufacture, t e molten metal being' then transferred to the combinationelectric furnace and intimately mixed with the refined Openhearthfurnace.-' For the melting of molten ferro chromium in the manner here-;serap, or a combination of scrap-and pig ,ironj'and refining the chargeby the aid of 'ffilectricgfurnaces-For the reduction of oxides fiomitsores and finally Y ilecarboniiing, deoxidizingand refining the as.coinpl 'eted'jnaterialst ,.For the reduction of ichromium oxidesfromitsi .oresl prefer to use an ,electric arc furnace, while to carry.outjthe final decarboniz'in g, deoxidizing and." refining proc- 'ess es,f-I;.u'se a combinatio nfelectric furnace in described and thefinalrefining and der' 1 oxidizing process proceeded with. 0 0

As herein stated the reduction and refining of chromium oxidefromores-is carried out in separate 'el'ectricfurnaces in-the presence-ofreducing agents-which maybe carbon, aluminium, silicon, calcium, calciumas silicid, calcium carbide, magnesium or the like. I mean by reducingagents any metal element or compound or, any mixture of these in anyproportion; whateven which, has or have the-propertyof ;reducing the"1.2

oxides or compounds of the combined metal or metals contained in theore; The rocess is accompanied by the evolution of eat.

I prefer to use a reducing agent consisting of a combination of theabove mentioned elements orcompounds reduced out in some form,preferably in the form of a ferro alloy of these agents crushed to passa ten mesh sieve and intimately mixed with the chromium ore and fluxingmaterials in such quantities or precentages as to ensure decarbonizingand refining. A slag 'ng mixture of a basic nature composed of ime andfluorspar may be employed in this stage of the process. I prefer,however, to use a neutralized slagging mixture and to this end silica orhighly silicious material may be added to a slagging mixture such asthat referred to, to secure the desired degree of neutrality.

I have discovered by numerous experiments that a neutralized slag with acovering of a substance rich in titanic oxide (TiO for example, rutile,if applied thereto eliminates the hi h chromium oxide losses in the slagot erwise experienced when a purely basic slag is employed while at thesame time eliminates carbon, silicon, sulphur and phosphorus to a markeddegree together with the production of a slag of increased fiuidit andfusibility. The temperature of the' urnace is raised to form theneutralized slag as quickly as possible by the aid of the upperelectrodes. When the slag is fused a rich in titanic oxide is thrownevenly over its surface andby continued heating the ti-. tanic oxidebecomes thoroughly incorporat-- ed with the other slagging materials.The

combination electric furnace is then operated by using the bottomelectrode setting 11?) a constant flow of metal under the'slag. errochromium containing a variable amount of carbon for instance, 1% to 6%may be employed 1f melted and subjected to the refining process asdescribed above. The resultant refining sla is withdrawn from thefurnace on comp etion of the refining process crushed and passed throughthe electric smelting furnace as raw material and quantity of thesubstance,

slagging mixture for fluxin the initial reduction of chromium ore. lyadopting this method the actual loss of chromium is ex-' tremely small.On completion the refined ferro chromium is intimately mixed with therefined iron in a separate combination electric furnace in suchquantities or proportions to give the desired percentages in thecompleted material. A calicum carbide slag is formed and the furnace isoperated by using the bottom electrode and a thoroughly homogeneousdeoxidized metal will be obtained Without additional stirring orrabbling.

Refined iron taken from the basic open hearth furnace may be employed asa base and the process proceeded with as herein described.

One method I employ for the production of rustless iron or stainlesssteel is to refine a charge or iron in the basic open hearth furnace andintimately mix the same with a desired proportion of refined moltenferro chromiumin a hot ladle.

By employing the continuous method in the manner herein described athoroughly homogeneous alloy can be produced containing any desiredpercentage of chromium,

carbon, metals and metalloids to suit re quirements.

As variations may be made in the alloy herein set forth withoutdeparting from the scope of this invention, it is to be understood thatit is herein described as illustrat-ive rather than in a limiting sense.

Having now described the nature of my invention what I claim as new is:

1. The method of producing a rustless iron alIoy which consists inproducing molten iron and partially refining the same, reducing themetal oxides of chromium ore, and

refining the resultant metal in an electricfurnace bythe aid of suitablereducing and refining agents, transferring the molten iron andferro-chromium to a separate combination are and resistance electricfurnace, and subjecting the combined charge to a final mixing, andrefining and. deoxidizing process at one and the same time.

2. The method of producing a rustless iron alloy which consists in firstmelting crude iron, partially refining the molten metal in an'openhearth furnace, reducing the metal oxides of chromium ore and refiningthe resultant metal in an electric furnace by the aid of suitablereducing and refining agents, transferring the molten iron andferrochromium to a, separate combination are and resistance electricfurnace, subjectin the combined charge to a final mixing, re ing anddeoxidi'zing process at one and the same time 1n the presence ofa-deoxidizing slag. 3. The methhd of producing fen-o-chromium low incarbon and silicon by reducing the metal oxides of chromium ore withsuitloc slag rich in silicious or titanic material thereby eliminatingheavy chromium oxide losses.

4. The method of producing neutralized slag containing lime andfluorspar which consists in adding thereto, after the sla is fused, ahighly silicious material toget er with a quantity of a substance richin titanic oxide.-

' 5. The method of producing rustless iron alloy by a continuous directprocess, from crude iron which consists in melting andparti-allyrefining the same in a suitable fur nace, reducing the metaloxides of chromium ore and partially refining the resultant metal in anelectric furnace in the presence of reducing and refining agents, thusforming a slag, neutralizing and saturating the slag by adding theretosilicious or titanic materials, removing the neutralized slag andbringing the molten chromium and iron mixtures together in a separatecombination are and resistance electric furnace and subjecting thecombined mixtures to a finaimixing,

refining and. deoxidizing process.

6. The method of producing a rustless iron alloy which consists inproducing molten iron and partially refining the same, reducing themetal oxides of chromium ore in an electric furnace by the aid ofsuitable reducing and refining agents, thus forming a slag, neutralizingand saturating the slag by adding thereto, a substance rich in siliciousor titanic oxides, removing the neutralized slag, mixing, refining anddeoxidizing the molten chromium and iron mixture and using the removedslag as a fluxing medium, and a chromium oxide supply in the subsequentreduction of chromium ores.

In testimony whereof I hereunto afiix my signature.

WILSON BENNETT.

